The invention relates generally to lights or lanterns that incorporate light-emitting diodes (LEDs) as a light source.
Conventional lighting systems typically utilize an incandescent bulb as a light source. However, incandescent bulbs have a relatively short operating-life, tending to burn out as their filaments quickly become brittle and weaken due to aging and vibration. The consequential necessity for replacement of expired incandescent bulbs on a frequent basis is both expensive and time-consuming. Additionally, where colored light emission is needed, incandescent lights also require colored lenses, which decrease light transmission and often fade due to weathering and ultraviolet radiation. In contrast to incandescent bulbs, light emitting diodes (LEDs) are light sources with a long operating-life, and are able to generate light of various colors without the need for a colored lens. Furthermore, LEDs require low power to operate, are small in size, demand very low current, and are resistant to shock and vibration. For these reasons, LEDs are desirable light sources in flashlights, lanterns and similar lighting applications.
Optimally, the light emission path provided by a lantern covers an arc of 360-degrees, therefore making it desirable to use an onmidirectional light source placed in the center of a magnifying lens to project light and provide illumination. While incandescent bulbs are omnidirectional, LEDs are not. Nevertheless, for the reasons above stated, it is advantageous in other respects to utilize LEDs as light sources in lighting applications.
Early versions of lighting applications utilizing LEDs were marginally effective due to the low light-emitting energy and luminance provided by the LEDs. To overcome this limitation and address the need for an omnidirectional light source, one prior art lighting device places a multitude of LEDs projecting from a cylindrical support member, so that LED light is projected outward over a 360-degree arc. Another prior art lighting device projects LED light emitted from a multitude of planar-mounted LEDs toward a reflector positioned so as to redirect the light in a 360-degree arc parallel to the planar mounted LEDs. As in many conventional lighting applications, light from an LED array may also be passed through a magnifying lens to further distribute emitted and/or reflected light.
Unfortunately, the above mentioned attempts to construct a commercially viable lighting application utilizing LEDs still suffer from many disadvantages. In order to provide the required illumination, the prior art requires a large number of LEDs. Consequently, such a lighting application has excessive power consumption and an undesirably short operating-life during battery-powered operation. In contrast, the commercial requirement of a highly intense and efficient lighting device coupled with the limitations of LED light sources and the need for reasonable power consumption dictates that the energy in the visible spectrum be generated and utilized as efficiently as possible. In addition, depending on the lighting, application, generated light may be required to be focused in various desired directions. For example, in a beacon lighting system utilized to provide navigational aid, light must be directed at various up-angles. Despite these needs, prior art lighting applications fail to provide the desired efficiency or an easy adjustment method that allows light to be directed in a particular desired direction, for example, at a particular up-angle.
Accordingly, it is an objective of the invention to provide a compact and efficient lantern utilizing an arrangement of a minimal number of LEDs as a light source. It is also an objective of the invention to collect, direct and magnify the light generated by an such a minimal arrangement of LED light sources so as to maximize provided illumination and visibility. It is a further objective of the invention to provide a directional lighting device that is capable of being easily adjusted to supply light in a predetermined arc at various up-angles.
To that end, a lantern is provided that utilizes an arrangement of a minimal number of LEDs and a conical reflector to create a light source having a light source image with sufficient intensity to supply illumination in the intended lighting conditions. The conical reflector of the invention is positioned with its axis approximately orthogonal to a planar surface and the vertex of the conical reflector facing the planar surface. Arranged on the planar surface at a radial distance from the point of intersection with that surface of the axis of the conical reflector, LEDs are positioned around a 360-degree arc, with each LED equally spaced from adjacent LEDs on the arc. The radius of the circular arrangement of LEDs is smaller than the largest radius of the conical reflector and all LEDs are positioned to emit light toward the conical reflector in a direction perpendicular to the planar surface. By appropriate selection of the cone angle for the conical reflector and the distance between the LEDs and the conical reflector, the light source image may be positioned on the axis of the reflector. The cone-shape of the conical reflector also enables light that is incident the reflector, and thus reflected, to strike the reflector at horizontal angles beyond the light spread offered by an LED. In this manner, a 360-degree arc of light may be created using LEDs with small light spreads. In an exemplary case, a 45-degree conical reflector may be selected such that light produced by a minimum of only four LEDs with 30-degree light spreads may be redirected to create a 360-degree arc of light outward from the conical reflector.
Both the planar mounted LEDs and the conical reflector are surrounded by a transparent magnifying lens that concentrates the light produced in the 360-degree arc. Each of the planar surface, conical reflector and magnifying lens may be formed of molded plastic and joined to a relatively rigid base assembly that supports the lantern in an upright position. The distance between the planar surface and the conical reflector may be adjusted in order to vary the position of the light source image off the axis of the conical reflector, thereby directing the arc of light generated by the LEDs at various up-angles. For this purpose, the base assembly has a plurality of mounting positions that allow the planar surface (and thus the LEDs) to be secured at various predetermined distances from the conical reflector. Positioning the planar surface at a predetermined mounting positions results in the light generated by the lantern being directed at a corresponding predetermined up-angle. The base assembly may also house a power source and a control circuit for management of the application of power that illuminates the lantern.